Exemplary embodiments pertain to the art of electric machines and, more particularly, to a rotor for an electric machine.
Many electric machines include a stator and a rotor. The rotor spins relative to the stator in response to an electrical current. Electric motors and generators are both examples of electric machines. An electric motor uses electrical energy to produce mechanical energy, typically through the interaction of magnetic fields and current-carrying conductors. Conversely, a generator produces electrical energy from mechanical energy.
The rotor may be formed of multiple parts. For instance, the rotor may include a hub through which a rod is passed. The rod engages the hub. The hub is typically surrounded by a rotor lamination. The rotor lamination may include magnets or wires disposed therein. Regardless, in the case of a motor, a current is applied to the stator which causes the rotor to turn. This causes the rod to turn and produce mechanical energy.
During operation, heat may cause portions of the rotor to expand. The heat may be caused due to electrical current passing through the rotor and stator. Some environments, such as an automobile engine, may experience high temperature swings and these swings may cause the rotor to expand.
Regardless of the cause, heat related rotor expansion may limit the materials used in rotor construction. In particular, heat expansion may require that the hub and the lamination be formed of the same or similar material. This requirement is due to stress that may be created if one of the portions expands due to heat (or motion) at a different rate than another portion.